Liquid containment tanks or containers are used in a number of industrial processes such as food manufacturing, pharmaceutical manufacturing, chemical processing, material fermentation and so on. It is often critical to ensure that the interior of the tank is free of unwanted debris and contaminants. For example, a tank that is typically filled to a certain level may exhibit a “tub ring” about its interior circumference at the level to which the tank is most often filled. Also, various equipment within a tank, tank inlets and outlets etc. may trap sediment or debris that may later reenter the tank contents during use.
Unwanted contaminants in the tank may negatively impact the quality of the finished product being manufactured or processed. Also, the interior of a tank must be properly cleaned if regulations relevant to certain industries such as pharmaceutical processing shall be followed. Thus, it is common to clean the interior of such tanks at certain intervals, e.g. after each process batch, to ensure product quality and adherence to any relevant regulations.
Tank cleaning systems are available that clean debris and residue from the interior of tanks and other vessels through the use of what is commonly known as impingement cleaning. One common type of such systems employs a cleaning apparatus that is inserted into the tank and which has a hose or pipe that extends into the tank. At an innermost end of the pipe a rotary jet head is affixed. The rotary jet head is rotatable about one or two axes and, in the latter case, is typically geared such that as the jet head rotates about an axis of the pipe, it also turns upon an axis perpendicular to the pipe.
A relationship between rotations about two axes depends on a gearing ratio, which is selected such that a combination of a particular orientation and position of the jet head repeats only after multiple revolutions around the axis of the pipe. This technique staggers subsequent traces of the spray against a tank interior on each revolution of the rotary head to ensure that substantially every portion of the tank interior is exposed to the cleaning spray at some time during the cleaning process. The accomplished traces of the spray against the tank provides a cleaning apparatus that sprays cleaning liquid in a predetermined pattern on the interior surface of the tank.
To ensure that the interior of a tank is adequately cleaned the cleaning liquid should be sprayed in the predetermined pattern. Alternatively, a cleaning duration may be prolonged, which however may lead to excessive waste of time, cleaning fluid, and energy.
To ensure adequate cleaning while still avoiding excessive waste some different techniques have been employed. For example, patent document US 2008/0142042 A1 discloses a tank cleaning system that allows for a cleaning process to be monitored and provides a cleaning validation. This is done by automatically accounting for characteristics of a tank being cleaned and by modifying the cleaning operation accordingly. Patent document WO2010/117324 A1, on the other hand, discloses how cleaning is improved by a liquid ejection nozzle that regularly sprays the pipe that extends into the tank.
The cleaning apparatus may also be used for mixing a content of the tank. This is typically done by filling the tank with the content until the rotary jet head is fully underneath a surface of the content. The content is then mixed by circulating it from an outlet of the tank and back into the tank via the rotary jet head. As with cleaning, mixing must be adequately performed and it is important that this may be done without e.g. excessive circulation of content. When a tank cleaning apparatus is capable of also performing mixing of a content of the tank, the apparatus is often referred to as a liquid ejection apparatus.
Present techniques ensure in some cases that cleaning of the interior of tanks and/or mixing of a content of a tank is accomplished while still ensuring that cleaning or mixing time and use of cleaning resources like various detergents are kept at a low level. However, there may be problems in some cases, for example because of the size and shape of the tank, the type of substance to be cleaned of from the tank interior or mixed in the tank, varying climate conditions in the environment surrounding the tank, irregular or deficient behavior of components cooperating with the liquid ejection apparatus etc. Thus, it is estimated that improvements may be made in respect of reducing time and resources required for obtaining proper cleaning and/or mixing.